President Obama's approval numbers are down, and voters tend to punish commanders-in-chief in the sixth year of their terms. So it's unlikely that Obama -- and Democrats -- will get the credit on Michigan's economy.

But there are some storm clouds amidst the recovery. A new Pew Charitable Trusts report shows that Michigan's tax revenue has yet to rebound to its pre-recession level.

Our tax collections are still down 11.2 percent. Only five states are faring worse -- Louisiana, Alaska, Georgia, Florida and Wyoming. The national average has revenues coming in 2.2 percent above 2008 levels.

This doesn't exactly come as a surprise, as Michigan saw this year's surplus chopped in half. One of the main culprits was a bill Snyder signed making it harder to go after those responsible for deadbeat corporations, which comes with an estimated $280 million hit to state revenue.

Michigan also has embarked on big business tax cuts -- the new corporate income tax is roughly worth $2 billion. That's partially offset by a $1.4 billion tax increase to individuals, but it's not revenue-neutral.

The Wolverine State also lags behind all states in the Midwest/Great Lakes region. The big winners are Minnesota (+20.6 percent) and Illinois (+23.4 percent), although the Land of Lincoln's income tax hike (which is responsible for much of its growth) is tied up in court.

Other nearby states are experiencing modest growth, like Indiana (+3.8 percent) and Wisconsin (+3.6 percent). Ohio is still in negative territory, like us, with revenues 7.9 percent lower than they were six years ago.

A total of 26 states haven't had revenues bounce back completely since 2008 -- which demonstrates how uneven the recovery has been.

New Jersey Gov. Chris Christie, a likely 2016 GOP presidential hopeful, is struggling with 10.7 percent less revenue than pre-recession and a $2.7 billion, two-year deficit. The state's credit rating has been downgraded six times.

Meanwhile, the Pew report notes that blue states like Minnesota, New York and California are "raking in tax revenue and churning out new jobs at a pace exceeding pre-recession levels."

California (+4.2 percent), the right's boogeyman of liberal excess, is nursing a $4 billion surplus. New York (+9 percent) has enough to dole out a $1 billion property tax cut. Minnesota, as MLive columnist Rick Haglund notes, has the strongest economy in the Great Lakes region.

Of course, conservatives and libertarians typically celebrate when states' bank accounts run dry. That means it's time to cut taxes and government, which, coincidentally, they argue we must do in boom times, as well.

But Haglund rightly argues that higher taxes enable states like Minnesota to "adequately fund education, transportation and other quality of life investments that are needed to thrive in a knowledge economy."

There's a reason why Michigan voters have told politicians to scrap a tax cut -- we want you to fix our crummy roads.

But that takes money. And in Michigan, it's in short supply.

Susan J. Demas is Publisher and Editor of Inside Michigan Politics, a nationally acclaimed, biweekly political newsletter. She can be reached at susan@sjdemas.com. Follow her on Twitter here.